The ISC 200 Series Pulleys are redesigned versions of the popular ISC arborist blocks with a new SafeLock mechanism and improved strength. Using state-of-the-art stress analysis programs, the hot-forged aluminum frames are optimized for the forces arborists put on their blocks, and the unique axle and frame interlocking design using heat-treated hardened steel axles means that these pulleys are up to 150% stronger than their predecessors. The Patent Pending SafeLock system is an updated version of the ISC SpringLock design that provides an extremely low profile along with the same quick opening action. Anodized finish. Weighs 4.1 lbs. MBS: 56,202 lbs. (250kN). Maximum rope diameter: 5/8" (16mm). Standards Met: CE Machinery Directive 2006/42/EC, UKCA Supply of Machinery (Safety) Regulations 2008.